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The Greenland shark ( Somniosus microcephalus), also known as the gurry shark or grey shark, is a large shark of the family Somniosidae ("sleeper sharks"), closely related to the Pacific and southern sleeper sharks. Inhabiting the North Atlantic and , they are notable for their exceptional longevity, although they are poorly studied due to the depth and remoteness of their natural habitat.
Greenland sharks have the longest lifespan of any known vertebrate, estimated to be between 250 and 500 years. They are among the largest extant shark species, reaching a maximum confirmed length of long and weighing over . They reach sexual maturity at about 150 years of age, and their pups are born alive after an estimated gestation period of 8 to 18 years. The shark is a generalist feeder, consuming a variety of available foods, including carrion.
Greenland shark meat is Toxicity to mammals due to its high levels of trimethylamine N-oxide, although a treated form of it is eaten in Iceland as a delicacy known as kæstur hákarl. (2025). 9780313380594, Bloomsbury Publishing USA. ISBN 9780313380594 Because they live deep in remote parts of the northern oceans, Greenland sharks are not considered a threat to humans. A possible Shark attack occurred in August 1936 on two British fishermen, but the species was never identified.
The Greenland shark is a thickset species, with a short, rounded snout, small eyes, and small dorsal and pectoral fins. The gill openings are very small for the species' great size. Female Greenland sharks are typically larger than males, with males reaching maturity at a smaller size than females. Coloration can range from pale creamy-gray to blackish-brown and the body is typically uniform in color, though whitish spots or faint dark streaks are occasionally seen on the back.
The shark is often infested by the copepod Ommatokoita, a crustacean which attaches itself to the shark's eyes. It was speculated that the copepod may display bioluminescence and thus attract prey for the shark in a mutualistic relationship, but this hypothesis has not been verified. These parasites can cause several damages to the sharks' eyes, such as ulceration, mineralization, and oedema of the cornea, leading to almost complete blindness. This does not seem to reduce the life expectancy or predatory ability of Greenland sharks, due to their strong reliance on smell and hearing.
The genome of the Greenland shark was published in 2024. It is 6.45 Gb (billion ) in length.
The 48 to 52 lower teeth are interlocking, broad and square in shape, containing short, smooth cusps that point outward. Teeth in the two halves of the lower jaw are strongly pitched in opposite directions.
The blood of Greenland sharks contains three major types of hemoglobin, made up of two copies of globin combined with two copies of three very similar subunits. These three types show very similar oxygenation and carbonylation properties, which are unaffected by urea, an important compound in marine elasmobranchii physiology. They display identical electronic absorption and resonance in Raman spectroscopy, indicating that their heme-pocket structures are identical or highly similar. The hemoglobins also have a lower affinity for oxygen compared to temperate sharks. These characteristics are interpreted as adaptations to living at great water depths.
/ref> The largest of these sharks were found having eaten Acadian redfish, as well as other higher trophic level prey.
It is proposed that, because of their slow speeds and low twitch speed muscle fiber, Greenland sharks hunt marine mammals, such as seals and smaller cetaceans, that are asleep, injured, or sick, as well as scavenging. Regarding most benthic prey, they utilize their cryptic coloration, approaching prey undetected before closing the remaining distance. Once they get close to their prey, Greenland sharks expand their buccal cavity to suction feeding, drawing in prey. This suction mechanism is the likely explanation for why the gut contents of Greenland sharks are often of whole prey specimens.
Greenland sharks have also been found with remains of moose, horse, and reindeer (in one case an entire reindeer carcass) in their stomachs. Polar bear remains have also been recovered, though these are thought to be of bears that died from other causes. The Greenland shark is known to be a scavenger and is attracted by the smell of rotting meat in the water. The sharks have frequently been observed lurking around fishing boats and herds of seal.
Although such a large shark could easily consume a human swimmer, the frigid waters it typically inhabits make the likelihood of attacks on people very low. To date there exists only one report of human predation by a Greenland shark. Around 1859 in Pond Inlet, Canada, it was reported that a Greenland shark was caught containing a human leg in its stomach. This story, however, was never scientifically investigated and remains unverified.
Genetic evidence suggests that Greenland sharks historically inhabited deep-sea environments, ranging across pan-oceanic regions at depths greater than 1,000 meters. During the Quaternary, global cooling influenced thickening sea ice and submerged Arctic landscapes, which likely isolated connectivity between the sharks. However, fluctuating glacial cycles periodically opened opportunities for population mixing, impacting migration patterns and genetic diversity. Today, Greenland sharks are found not only in Arctic and sub-Arctic waters but also in regions further south, such as the Mid-Atlantic Ridge and the Gulf of Mexico.Grubs, Dean (15 August 2013). " Deep-C Scientists Capture First Greenland Shark in the Gulf of Mexico". deep-c.org These findings indicate a wider ecological range than previously thought.
In August 2013, researchers from Florida State University caught a Greenland shark in the Gulf of Mexico at a depth of , where the water temperature was .Grubs, Dean (15 August 2013). " Deep-C Scientists Capture First Greenland Shark in the Gulf of Mexico". deep-c.org Four previous records of Greenland shark were reported from Cuba and the northern Gulf of Mexico. A more typical depth range is , with the species often occurring in relatively shallow waters in the far north and deeper in the southern part of its range.
In April 2022, a large Somniosus shark was caught and subsequently released on Glover's Reef off the coast of Belize. This shark was identified as being either a Greenland shark or hybrid; Greenland × Pacific sleeper shark. This observation is notable for being the first possible record of a Greenland shark from the Western Caribbean, and being caught on a nearshore coral reef (the only other record of this species from the Caribbean was made from a deep-water habitat off the Caribbean coast of Colombia). The discovery indicates that Greenland sharks may have a wider distribution in the tropics, primarily at greater depths, than previously believed.
Estimates of litter size have varied across studies. Some studies suggest that this species produce up to 10 pups per litter, each initially measuring some in length. Based on these estimates, it is thought that Greenland sharks can have between 200 and 700 pups during their lifetime. Within a Greenland shark's uterus, villi serve a key function in supplying oxygen to embryos. It is speculated that oxygen supply is a major limiting factor in the size of litters.
Other studies, however, which take into account ovarian data and analysis of other Squaliform shark species, have estimated that Greenland sharks may produce from 200 to 324 pups per litter, each pup measuring between in length. The same study also confirms that Greenland shark embyros develop inside the uterus without a placenta.
The shark is likely affected by quantity, dynamics, and distribution of Arctic sea ice. The rate of projected loss of sea ice will continue to negatively influence the abundance, distribution and availability of prey, while, at the same time, providing greater access for fishing fleets. There is greater potential for new fisheries to develop as more productive and abundant southerly species invade the warming Arctic waters.
Greenland shark meat is produced and eaten in Iceland where, today, it is known as a delicacy called hákarl. To make the shark safe for human consumption, it is first fermented and then dried in a process that can take multiple months. The shark was traditionally fermented by burying the meat in gravel pits near the ocean for at least several weeks. In the present day, shark cuts are typically fermented in containers that are perforated to allow liquid to drain. The fermentation process converts urea into ammonia and TMAO into TMA, which then drains as liquid from the meat. The meat is then excavated and hung in strips to dry for several more months.
The Greenland shark plays a role in cosmologies of the Inuit from the Canadian Eastern Arctic and Greenland. Igloolik Inuit believe that the shark lives within the urine pot of Sedna, goddess of the sea, and consequently, its flesh has a urine-like smell and acts as a helping spirit to shamans.
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